Agilent Technologies HSSI WanProbe J3916A - Manual (Page 164)

Glossary
144
Network Layer
Level 3 of the seven level OSI reference model defined by ISO. This layer
provides the routing of data through the network based on global addresses.
Typical examples are IP and X.25.
Nibble
A nibble is four bits.
NRZI (Non-Return to Zero Invert)
Level 1 encoding mechanism in which a binary state is represented by a change of
the level 1 signal condition. The other binary state is represented by a continuation
of the level 1 signal. In wide area networking, the most common implementation
of NRZI encoding is an option in IBM’s SDLC. In this case, a 0 is represented by
a change in the level 1 signal. A binary 1 is represented by a continuation of the
signal. In conjunction with a bit oriented level 2 link protocol, proper clocking
may be derived by the receiver independent of DCE clocking.
Object
Any device that can be monitored or controlled by use of the SNMP protocol.
Octet
8 bits considered as a transmission element. Octets in general are not equivalent to
user’s data bytes. “Octet” is more general than “Byte,” allowing for smaller
elements to be contained (1 bit fields, 2 bit fields, and so forth.)
Octet
The common term used for a collection of 8 bits is a byte. In some cases, the term
used is an octet. Although many people use these terms interchangeably, there are
a few differences. The bits of a byte are normally numbered from 0 to 7. The bits
of an octet are generally numbered from 1 to 8. While the 4th bit of both a byte
and an octet are the same, bit 4 of each is a different bit.
OSI
Open Systems Interconnect. The 7 level communications structure promoted by
ISO.